Re: xfstests 073 regression

Dave Chinner
2011-08-02T12:04:57Z

On Tue, Aug 02, 2011 at 07:44:28PM +0800, Wu Fengguang wrote:
> On Tue, Aug 02, 2011 at 12:52:42AM +0800, Christoph Hellwig wrote:
> > wb_check_background_flush is indeed what we're hitting.
>
> That means s_umount is NOT held by another queued writeback work.

Right. We already kind of knew that was ocurring because there's
a remount,ro going on.

>
> > See the trace output using a patch inspired by Curt's below:
> >
> > # tracer: nop
> > #
> > # TASK-PID CPU# TIMESTAMP FUNCTION
> > # | | | | |
> > <...>-4279 [000] 113.034052: writeback_grab_super_failed: bdi 7:0: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=wb_check_background_flush
> > <...>-4279 [000] 113.034052: writeback_grab_super_failed: bdi 7:0: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=wb_check_background_flush
> > <...>-4279 [000] 113.034052: writeback_grab_super_failed: bdi 7:0: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=wb_check_background_flush
>
> What's that bdi 7:0? And sb_dev=0:0, nr_pages=9223372036854775807=0x7fffffffffffffff.
>
> All are indicating some special bdi/inode.

#define LOOP_MAJOR 7

It's a loop device. xfstests uses them quite a lot.

Maybe it would be a good idea to run xfstests on an xfs filesystem
in your regular writeback testing cycle to get decent coverage of
this case?

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com